Information has two aspects: a quantity to be called "extent" and a quality which may be termed "content" since it deals with meaning. The latter originates via selective self-organization which can be described also in quantitative physical terms. A prerequisite is the reproducibility of the informational substrate forming the basis of selection. This paper focuses on selection being the analogue of a physical phase transition. In the first part the criteria for phase transitions are formulated. The second part introduces the concept of information space and describes information as selected points or regions in this space. In the third part selection is analysed in terms of the criteria for phase transitions, and finally the concept is confronted with experimental data. The conclusion is reached that information content is generated via selection which can be described as a phase transition in information space.